Azido-PEG1-NHS ester

Azido-PEG1-NHS ester is a bifunctional PEG-based linker designed for modular PROTAC assembly, combining an NHS-activated ester for efficient conjugation to amine-bearing ligands with a terminal azide handle for orthogonal “click” functionalization. Its flexible PEG segment can improve solubility and reduce steric constraints during ternary complex formation. The azide enables robust downstream attachment of complementary moieties, facilitating streamlined synthesis of targeted protein degraders.

Structure: The molecule contains a polyethylene glycol spacer bearing an NHS ester and a terminal azide. It features an activated carboxylate within an N-hydroxysuccinimide leaving group, connected through an ester linkage, and an azide functional group suitable for cycloaddition chemistry. The PEG segment provides conformational flexibility and enhanced hydrophilicity.

Reactivity: The NHS ester reacts with primary amines under mildly basic aqueous or mixed solvent conditions to form stable amide bonds, typically using buffered systems to control hydrolysis. The azide undergoes copper-catalyzed azide–alkyne cycloaddition or related azide click reactions with appropriate partner groups. Reaction design should consider NHS ester stability, minimize aqueous exposure prior to conjugation, and select solvents compatible with both coupling and click steps.